Why Does Copper Turn Green Over Time? 10 Secret Facts About Statue Of Liberty
Copper naturally turns green over time as it reacts with oxygen in the air – a chemical reaction known as oxidation. The green colour is simply the natural shade of the patina that forms over the copper surface; the patina protects the copper from deterioration and creates a light bluish-green facade which can be seen on many copper rooftops and copper structures.
Copper doesn’t turn green overnight, it transitions through a number of stages over the years, moving from its initial orange shade into a dull brown colour, before finally settling into the familiar green tint.
To demonstrate the timescale of this transition, we’ve used the most famous and iconic example of this process on Earth: the Statue of Liberty. The animation below tracks its changing colour pallette over the months and years since it was first installed on what is now known as Liberty Island:
The patina which forms over copper works to protect and preserve the underlying copper material. This is different to what happens to iron during oxidation, where rust forms over the surface, deteriorating the material over time.
